One-Pot Zinc-Promoted Asymmetric Alkynylation/Brook-Type Rearrangement/Ene–Allene Cyclization: Highly Selective Formation of Three New Bonds and Two Stereocenters in Acyclic Systems

by Polina Smirnov, Jomon Mathew, Anne Nijs, Einat Katan, Miriam Karni, Carsten Bolm, Yitzhak Apeloig, Ilan Marek*

It’s as easy as 1, 2, 3: In a one-pot sequence, two stereocenters and three new bonds were created with high selectivity through an asymmetric alkynylation of acyl silanes, a tandem Brook-type rearrangement and Zn–ene–allene cyclization, the addition of an electrophile, and finally oxidation (see scheme). The straightforward nature of the synthetic procedure contrasts strongly with the complexity of the densely functionalized products obtained.

Angewandte Chemie Internation Edition

Article first published online: 23 OCT 2013

DOI: 10.1002/anie.201306749

Organoytterbium Ate Complexes Extend the Value of Cyclobutenediones as Isoprene Equivalents

by Emma Packard, David D. Pascoe, Jacques Maddaluno, Théo P. Gonçalves, David C. Harrowven*

Changing course: While organolithium and Grignard reagents favor addition to C1 of A (R=Me), the corresponding organoytterbium reagents add to C2 (R=tBu). Computational studies provide insights into the nature of organoytterbium species and their reactivity, and a total synthesis of (−)-mansonone B illustrates the utility of the method in terpenoid synthesis. Tf=trifluoromethanesulfonyl.

Angewandte Chemie Internation Edition

Article first published online: 23 OCT 2013

DOI: 10.1002/anie.201307193

Palladium(II)-Catalyzed Intramolecular Hydroamination of 1,3-Dienes to Give Homoallylic Amines

by Justin M. Pierson, Erica L. Ingalls, Richard D. Vo, Forrest E. Michael*

A pincer for high selectivity: A mild palladium-catalyzed hydroamination of protected amino-1,3-dienes has been developed. This highly regioselective reaction employs a tridentate PNP pincer ligand and leads to cyclic and homoallylic protected amines in high yields. Substrates with a wide array of amine protecting groups and diene substitution patterns were cyclized to form five- and six-membered heterocycles. PG=protecting group.

Angewandte Chemie Internation Edition

Article first published online: 24 OCT 2013

DOI: 10.1002/anie.201305766

Cu(OTf)2-Mediated Fluorination of Aryltrifluoroborates with Potassium Fluoride

by Yingda Ye, Sydonie D. Schimler, Patrick S. Hanley and Melanie S. Sanford*

This Communication describes the Cu(OTf)₂-mediated fluorination of aryltrifluoroborates with KF. The reaction proceeds under mild conditions (at 60 °C over 20 h) and shows a broad substrate scope and functional group tolerance. The Cu is proposed to play two separate roles in this transformation: (1) as a mediator for the aryl–F coupling and (2) as an oxidant for accessing a proposed Cu^III(aryl)(F) intermediate.

Journal of the American Chemical Society

Publication Date (Web): October 25, 2013

DOI: 10.1021/ja408607r

Oxidant-Free Conversion of Primary Amines to Nitriles

by Kuei-Nin T. Tseng, Andrew M. Rizzi and Nathaniel K. Szymczak*

An amide-derived NNN-Ru(II) hydride complex catalyzes oxidant-free, acceptorless, and chemoselective dehydrogenation of primary and secondary amines to the corresponding nitriles and imines with liberation of dihydrogen. The catalyst system tolerates oxidizable functionality and is selective for the dehydrogenation of primary amines (−CH₂NH₂) in the presence of amines without α-CH hydrogens.

Journal of the American Chemical Society

Publication Date (Web): October 21, 2013

DOI: 10.1021/ja409223a

Rhodium(III)-Catalyzed Indole Synthesis Using N–N Bond as an Internal Oxidant

by Baoqing Liu, Chao Song, Chao Sun, Shuguang Zhou and Jin Zhu*

We report herein a Rh(III)-catalyzed cyclization of N-nitrosoanilines with alkynes for streamlined synthesis of indoles. The synthetic protocol features a distinct internal oxidant, N–N bond, as a reactive handle for catalyst turnover, as well as a hitherto tantalizingly elusive intermolecular redox-neutral manifold, predicated upon C–H activation, for the formation of a five-membered azaheterocycle. The compatibility of seemingly dichotomous acidic and basic conditions ensures reaction versatility for multifarious synthetic contexts. The tolerance of an array of auxiliary functional groups potentially permits predefined, programmable substitution patterns to be incorporated into the indole scaffold. Comprehensive mechanistic studies, under acidic condition, support [RhCp*]²⁺ as generally the catalyst resting state (switchable to [RhCp*(OOC^tBu)]⁺ under certain circumstance) and C–H activation as the turnover-limiting step. Given the variety of covalent linkages available for the nitroso group, this labile functionality is likely to be harnessed as a generic handle for strikingly diverse coupling reactions.

Journal of the American Chemical Society

Publication Date (Web): October 7, 2013

DOI: 10.1021/ja408541c

Ruthenium Catalyzed Hydrohydroxyalkylation of Isoprene with Heteroaromatic Secondary Alcohols: Isolation and Reversible Formation of the Putative Metallacycle Intermediate

by Boyoung Y. Park, T. Patrick Montgomery, Victoria J. Garza and Michael J. Krische*

Heteroaromatic secondary alcohols react with isoprene to form products of hydrohydroxyalkylation in the presence of ruthenium(0) catalysts generated from Ru₃(CO)₁₂and tricyclohexylphosphine, enabling direct conversion of secondary to tertiary alcohols in the absence of premetalated reagents or stoichiometric byproducts. The putative oxaruthenacycle intermediate has been isolated and characterized, and reversible metallacycle formation has been demonstrated.

Journal of the American Chemical Society

Publication Date (Web): October 24, 2013

DOI: 10.1021/ja4087193

An Efficient Generation of a Functionalized Tertiary-Alkyl Radical for Copper-catalyzed Tertiary-Alkylative Mizoroki-Heck type Reaction

by Takashi Nishikata*, Yushi Noda, Ryo Fujimoto and Tomomi Sakashita

α-Halocarbonyl compounds undergo β-hydrogen elimination to give conjugated olefins in the presence of a transition-metal catalyst. However, a copper/triamine catalyst system can induce the alkylative Mizoroki–Heck reaction of styrenes with tertiary-alkyl halides possessing a withdrawing group under very mild conditions. This reaction provides an efficient synthetic methodology for tertiary-alkylated styrenes.

Journal of the American Chemical Society

Publication Date (Web): October 21, 2013

DOI: 10.1021/ja409661n